Hydrocarbon conversion process and apparatus



Jan. 6, 1959 c, o; BERG 2,867,580

HYDROCARBON CONVERSION PROCESS AND APPARATUS Filed May 11, 1956 UnitedSttes HYDROCARBON CONVERSION PROCESS AND APPARATUS Application May 11,1956, Serial No. 584,347 13 Claims. (Cl. 208165) This invention relatesto a continuous process and apparatus for the contacting of a fluid witha granular solid contact material and in particular relates to animproved process and apparatus for hydrocarbon conversions wherein ahydrocarbon stream is contacted with a stream of granular solid contactmaterial, such as a granular solid hydrocarbon conversion catalyst,which material is recirculated successively through a contacting orreaction zone and through a solids regeneration or reheating zone. Onespecific feature of the present inven tion is in the improved method andapparatus for control of the temperature of the reacting fluids passingthrough the downwardly moving bed of granular solid contact material inthe reaction zone, and for the control of the temperature ofregeneration of the spent contact material while passing it upwardly asa dense moving bed through a conveyance-regeneration zone concurrentlywith an oxygen-containing regeneration gas. In this invention, most ofthe liberated heat of regeneration is removed from theconveyance-regeneration zone directly as sensible heat of the spentconveyance-regeneration fluid.

atent o Hydrocarbon fractions in particular and many other fluidreactant streams in general are advantageously treated under reactionconditions of temperature and pressure in the presence of a solidgranular contact material, which may or may not have catalytic activity,to produce fluid products having improved properties. In the field ofpetroleum refining, hydrocarbon fractions normally boiling between thelimits of about 75 F. and about 1000 R, such as the light and heavynaphthas or gasolines and the light and heavy gas-oil fractions, aretreated at relatively high pressures and temperatures in the presence ofsolid contact materials to coke, crack, desulfurize, denitrogenate,hydrogenate, dehydrogenate, reform, aromatize, isomerize, or polymerizesuch hydrocarbon fractions to produce products having desirableproperties which particularly well suit them for hydrocarbon crackingfeed, gasoline blending stock, solvents, or diesel or jet engine fuels,and the like.

In all of the foregoing processes which utilize a recirculating streamof solid contact material, the usual problems of transporting the solidswith minimum energy and without substantial attrition loss in asuperatmospheric temperature and pressure system are involved. In somecases separate contacting and regeneration vessels are employed whichrequire separate conveyance steps to transport the solids from thebottom of each vessel to the top of the other. In other cases theseprocesses are effected in a single column so that only a single solidstransport step is required, the regenerator and reactor being locatedone above the other in the column. The disadvantage of the formermodification is the necessity for two columns and the requirement fortwo separate solids handling steps. The principal disadvantage of thesecond modification is primarily structural in that with superimposedreaction and regeneration zones an excessively high mechanical structureis required, sometimes exceed:

ing 200 feet in elevation. A further disadvantage of the single columnoperation lies in the fact that the total conveyance distance is notmaterially dirferent from the total conveyance distance in thetwo-column modification.

Conventionally, the granular solids nave been conveyed for recirculationby mechanical elevators, by suspension in a conveyance fluid in thewell-known gas lift or pneumatic conveyance systems, and the like.Although the mechanical elevators operate with quite low energyrequirements, they are practically impossible to maintain at operatingtemperatures of around 1000 F. and at superatmospheric pressureconditions. Although the socalled gas-lift type of conveyor readilyoperates at superatmospheric pressures, tremendous quantities of liftgas are required in contacting systems recirculating contact material athigh solids to fluid ratios. in addition, the fact that the solidparticles move at relatively high velocities of the order of 50-100 feetper second and are free to impact the inner conveyor walls and eachother is the cause of an excessively high solids or catalyst attritionrate.

In the present invention, all separate conveyance steps as such havebeen eliminated because the solids are moved upwardly through theregeneration zone and are thus recycled.

In many contacting processes, a substantial change in temperature of thefluid occurs during passage through the contacting zone due toendothermic or exothermic reactions. For example, in gasoline reformingin the presence of hydrogen and a catalyst such as cobalt molybdate andproper temperature and pressure conditions, temperature decreases ashigh as F. occur in the conversion zone due to the endothermic nature ofthe hydrocarbon reactions which occur. The conventional equipment andprocess steps for compensating for such temperature changes are socomplex that few if any commercial solids-fluid contacting processeshave been designed, built, and operated to control them.

In the present invention, these temperature drops are eliminated usingheat liberated in the upflow regeneration step.

The present invention is therefore directed to an integratedsolids-fluid contacting process in which the conveyance and theregeneration and reaction zone temperature control problems indicatedabove are simultaneously eliminated by employing several novel andsimple process steps and apparatus.

It is a primary object of this invention to provide an improved processfor fluid-solids contacting operations in which granular solids arerecirculated and simultaneously treated to eifect a substantiallycomplete reheating or regeneration during a single conveyance step, andin which the conveyance distance is approximately one-half that usuallyrequired. I

It is also an object of this inventionto provide an improvedsolids-fluid contacting process in which effective control of fluidtemperature throughout the contacting zone is effected by the indirectdissipation of the liberated heat of regeneration.

A more specific object of this invention is to control the catalysttemperature in the conveyance-regeneration zone as well as thetemperature of the walls thereof and to control the temperature existingin the contacting or reaction zone by the step of recirculating aconveyanceregeneration fluid directly through the solid contact materialin the conveyance-regeneration zone and indirectly through a heatinterchange zone disposed within the reaction zone.

It is an additional object of this invention to provide an improvedapparatus for accomplishing the foregoing objects. I

rounded by a dense bed of solids to Other objects and advantages of thepresent invention will become apparent to those skilled in the art asthe description thereof proceeds.

Briefly, the present invention comprises an improved process andapparatus for the continuou s conta ctrng of reactive fluids withgranular solid Contact material in a reaction 'or conversion zone. Thegranular rnaterial, which may have catalytic properties, i'sirecir culated from the bottom of a reaction zone upwardly as substantiallycompact or dense-packed moving bed of granular solids through aregeneration zone and'is discharged therefrom in fully regenerated forminto the top of the reaction zone for reuse. i V l It is immediatelyapparent that the double conveyance required in the conventionalcontacting processes employing separate'r'egeneration and reactionvessels has been avoided and substituted with a solids upflowregenerate-r of less than half the distance heretofore required becausetheusually required sealing legs of great length used in gas-liftsuspension conveyances are eliminated. It is also apparent that thedistance for conveyance in this invention is reduced by more thanone-half from the distance required in the conventional processes usingsuperimposed reaction and regeneration zones and that accord ingly thephysical structure of the apparatus of this invention' has beensubstantially reduced with attendant economic savings. Spent granularSolids removed from the bottom of the reaction zone are moved upwardlyas a dense moving bed through the regeneration zone or conduit by emlsying a series of novel and critical steps. The spent granularsolidsare introduced into the regeneration zone in such a manner thatits inlet opening is submerged and surbe conveyed. This is convenientlydone by providing an induction zone or eharnbeninto which the solids.may be introduced at its upperend"and surrounding the inlet opening ofthe regeneration zone at a low point therein so that solids uponintroduction cover and submerge the inlet opening. Inn mediatel-yadjacent the'outlet opening of the regeneration zone, a means isprovided for applying a thrust or compacting force against the movingbed of regenerated and conveyed granular material discharging therefrom.This may be done in several ways including the disposition of a mesh orplate or cap immediately adjacent the outlet opening against which themoving bed of solidsflows and then reverses its direction. The sameresult may be obtained by discharging the solids in any directiondirectly into a chamber against a wallof the chamber or against a bed ofpreviously discharged solids so that the outlet opening is submerged bya bed of such solids. The solids may thus be discharged upwardly orhorizontally, or downwardly into such achamber to form a conical pile ofdischarged solids whose a ex intersects the outlet opening. The objectofthis step is to in some way restrict the discharge ofsolids at theoutlet opening without effecting any substantial restriction on thedischarge of regeneration fluid at the same point. "The granularmaterialin the regeneration line is thus prevented from becoming fluidized orsuspended in the regeneration fluid while it is moved. In this way themoving solids are maintained substantially at their static bulk density;that is, at the same bulk density as that offa downwardly movinggravity-packedbed; which inturn' is substantially the same as the bulkdensity of the solids when attest.-

The granular solids in this dense-packed form are caused to move bypassingja concurrent flow of regeneration fluid upwardly through theregenerationzone at a rate sufficient to overcome the opposing forces-ofgravity acting on the solids and also to overcome opposing forces offriction of regeneration. zone Wallsand thelike 'which' act against thesolids when they are conveyed. This fluid flows through theseriallyaconn ected intersticesof the dense-packed mass of, granularsolids which presents a high resistance elongated path 7 maintaining asubstantial pressure diflerential between the inlet and the outlet ofthe regeneration zone, a suflicient quantity of fluid is forced to flowtherethrough generating a more or less constant pressure gradient at allpoints along the length of the regeneration zone so as to apply a forceto the solids mass uniformly throughout the zone. The ratio of theresulting force tending to move :the solids upwardly to the forces ofgravity acting in the opposite direction has been termed the conveyanceforce ratio and is given by:

p COS 0 wherein is the pressure gradient in pounds per square foot perfoot of'regeneration zone length, p is the static bull: density of thegranular solids being conveyed in pounds per cubic foot, and 0 is theangular deviation of the direction of solids movement from an upwardvertical references axis. When the regeneration fluid flows at a ratesufficient to generate a pressure gradient which exceeds the forces ofgravity expressed by the term ccs 9) in Equation 1, a slightlyadditicnal flow of fluid is suflicient to ex-.eed opposing forces offriction and permit the solids to move continuously in dense or comgactform as an upwardly moving bed when a bed of solids is continuouslysupplied at the inlet and dense granular solids are continuouslywithdrawn at a controlled rate from the discharged mass of solids at theoutlet of the regeneration zone.

Because of the substantial pressure gradient characteristic of this formof solids movement and because of the fact that there is only arelatively minor pressure ditf-rential existing between the inlet andoutlet of a solidsfluid contacting vessel, it is apparent that thepresent regeneration system cannot be directly connected at both itsoutlet and inlet respectively to the solids inlet and outlet of thecontacting zone. In the present invention only one of the aforementionedconnections is made and the other connection is made indirectly througha gr:nu -ar solids pressuring vessel into which granular solids arecharged at a relatively low pressure, the vessel is sealed, highpressure fluid is injected to increase the pressure by an amountapproximating the characteristic pressure differential of theregeneration zone, and then. the solids are discharged at the higherpressure. If the inet to the regeneration zone communicates directlywith the outlet of the reaction zone,-this pressuring step is emplcyedtoreceive solids from the outlet of the regeneration Zone. and to pressurethem into the top of the reaction zone. When the outlet of theregeneration zone communicates directly with and at substantially thesame pressure as the reaction zone, the pressuring zone receives solidsat that pressure from the bottom of the reaction zone and pressures theminto the inlet ofthe regeneration zone as is illustrated in theaccompanying drawing. So far as the present invention is concerned, thepressuring step can be in any part of the cycle, that is; either beforeorafter regeneration.

The present invention is particularly well' adapted to the handling ofgranular solid materials in the wellknown hydrocarbon conversionprocesses mentioned above and in which a liquid or vaporizedhydrocarboniscontacted directly, With a moving mass; of contact'maeterial, usually having catalytic activity. During such processes,; thecatalyst ordinarily becomes deactivated after a variable period ofcontact and, is contaminated bya;hydrocarbonaceous deposit generallyreferred tov as whet? During-z the; regeneration; the; coked; catalyst:is.

treated with an oxygen-containing regeneration gas whereby thehydrocarbonaceous material is burned from the catalyst and the activityis restored. With most spent hydrocarbon conversion catalysts, theoxygen-containing regeneration gas will not initiate and sustaincombustion until the spent catalyst is raised in temperature to about700 F. Most hydrocarbon conversion catalysts also cannot be heatedduring regeneration to temperatures much above about 1200 F. and thespent conveyanceregeneration gas is'disengaged from the regeneratedcatalyst at temperatures below this value. These then are thetemperature limits within which the conveyance-re generation zone mustoperate when handling spent hydrocarbon conversion catalysts.

In the process of this invention, the removal of heat from theregeneration zone is by direct heat exchange and is efiected bymaintaining a recycle of regeneration gas upwardly through theregeneration zone and then through external heat interchange means,located in part within the reactor itself but out of contact with thesolids, and then back into the inlet of the zone- The regeneration gasis disengaged from the regenerated solids and discharged at the top ofthe unit at temperatures of the order of 1100 F. Ordinarily these gasescan only be cooled to a temperature which will initiate combustion ofthe hydrocarbonaceous spent solids, that is, about 700 F. However, inthe present invention a heat interchange step is effected along at leastthe first or lower part of the length of the regeneration zone itselfthereby maintaining low wall temperatures and permitting theregeneration gases to be cooled externally to temperatures considerablybelow this usual minimum temperature and then reheated at least to theminimum 700 P. value in the primary heat exchange-zone before the gasesare introduced into the regeneration zone inlet. This permits asubstantial decrease in the required diameter of the regenerator conduitwhich improves the heat transfer as well as a decrease in the quantityof regeneration gas recycle needed to remove the heat generated in theregeneration system. This is due to the fact that in'this specific typeof upflow regeneration the major portion of the coke burn-off occurs inthe lower or first portion of the regeneration zone and the minorportion of regeneration occurs in the upper regions of the zone.Accordingly the externally cooled regeneration gas is preheated fromwell below the spent catalyst ignition temperature by passing it aroundthe lower part of the regeneration zone whereby it cools the zone wallsand is heated to the temperature necessary to initiate combustion. It isthen introduced with the absorbed sensible heat directly into theregeneration zone for upward passage therethrough. Employing thistechnique has permitted reductions in regeneration fluid recycle of upto 75% because the recycle gas can herein readily be cooled from 1200"F. or higher to as low as 150 F. or lower (with condensate removalprovision) instead of only to the 700 F. figure mentioned above.

The external heat exchange means referred to above is comprised of twoessential parts. The first part consists of one or more indirect heatexchange means disposed out of contact with the solids inside thereactor column at one or more points between the feed inlet and theeffluent outlet. The spent regeneration gas is passed therethrough attemperatures of the order of 1000- 1200 F. to reheat indirectly thereactant vapor passing through the reactor. The flow rate is controlledto cornpensate for undesirable temperature decreases otherwise caused bythe endothermic nature of the hydrocarbon conversion reactionsoccurring. By this means, and in an apparatus more clearly described inconnection with the drawings, the reactant vapors are maintainedsubstantially at the desired reaction temperature throughout thereactor. In the case of combined desulfurization and reforming ofnaphtha this reaction temperature is between about 880 F. and 975 F.,the temperature may 6 average out at a constant value, or it may risewith distance from the inlet.

The second part of the heat exchange means is an interchanger in whichthe partially cooled regenerator off gases, after flowing through thereactor heater or heaters, are further cooled in exchange with the feedhydrocarbon and recycle hydrogen or both. Recycle hydrogen is used insuch hydrocarbon conversions as catalytic desulfurization,denitrogenation, deoxygenation, reforming, hydrocracking, isomerization,and the like. In this exchanger the partially cooled regenerator offgases are further cooled to dissipate the remaining heat liberatedduring the catalyst regeneration. Due to these substantial increases inheat recovery, substantial reductions are provided in the heatingcapacity required to operate the contacting process in which thisinvention is employed. The present invention is therefore applicable toany recirculatory solids-fluid contacting process involving anexothermic regeneration of the contact material and an endothermicreaction such as reforming, cracking, etc. in the other contacting zone.Other specific applications will occur. to those skilled in the art fromthe present description.

The present invention will be more readily understood by reference tothe following description of the attached drawings in which:

Figurel shows a schematic flow diagram of the pro-cess of this inventionand a detailed elevation view in partial cross section of the reactionand regeneration apparatus, and I Figure 2 shows additional details ofthe reactor heaters.

The description is conducted in the form of a specific example of theinvention as applied to the continuous catalytic reforming anddesulfurization of a petroleum naphtha in the presence of hydrogencontaining recycle gas and a cobalt molybdate catalyst.

The permissible operating conditions for naphtha reforming anddesulfurization are from 700 to 1100 F., from 50 to 2000 p. s. i. g.,and from 500 to 10,000 s. c. fof hydrogen per barrel of naphtha feed.The following example gives the specific operating conditions of oneinstallation.

Rererring now more particularly to Figure 1, the apparatus consistsessentially of catalyst separator and pretreating chamber 10 into whichthe regenerated catalyst is discharged, naphtha reforming anddesulfurization column 12 through which the catalyst passes downwardlyas a moving bed by gravity, catalyst pressuring chamber 14 receivingspent catalyst from column 12, induction chamber 16 into which the spentpressured catalyst is discharged, and regeneration chamber 18 throughwhich the spent catalyst is moved upwardly and regenerated by means of aregeneration fluid flow, and the regenerated catalyst is discharged forpretreatment and recirculation into separator chamber 10.

The apparatus of this invention as shown is designed for the catalyticreforming and desulfurization of 1100' barrels per stream day of apetroleum naphtha having the following properties:

TABLE I Naphzha feed Boiling range, F 241-418 API gravity 46.3 Sulfur,weight percent 0.579 Nitrogen, weight percent 0.020 Knock rating (F-3)73.0 ASTM gum 45.0

at a temperature of 920 F. and a pressure of 405 p. s. i. go.

7 into naphtha engaging zone 28 in column 12. A primary stream ofrecycle gas containing hydrogen is introduced through primary recyclegas engaging zone 30 at a rate of 1700 MSCF. per day and at atemperature of 920 F. The mixture of naphtha vapor and hydrogen passesupwardly through primary reforming zone 32 countercurrent to thedownfiowing bed of cobalt'molybdate catalyst. Herein the cyclization ofparafi'in hydrocarbons takes place to form naphthenes and theendothermic aromatization of the naphthene hydrocarbons results in atemperature decrease. To maintain an approximately constant temperatureprofile throughout the reactor, one or more reactor heater zones 34 areprovided and through which regeneration zone off-gas is passed in anamount suflicient to reheat the vapors to about 920 F.,-or any otherdesired temperature. The

thus reheated mixture passes countercurrent to the catalyst throughsecondary reforming zone 36 wherein a further temperature decrease takesplace due to the endothermic aromatizationreactions. One or moreadditional reactor heater zones reheat this cooled mixture again toabout 920 F., or higher if an increasing temperature profile is desired.The mixture then continues upwardly through tertiary reforming zone 40from which the efliuent is removed from disengaging zone 42 at atemperature of about 880 F. and at 400 p. s. i. g. through line 44.

The eflluent vapor is passed through interchanger 46 wherein heat isrecovered in depropanizing the product and for preheating the naphthafeed and is thereby cooled to a temperature of 450 F. which is justsufficiently below the dew point of the effluent to effect a partialcondensation of polymeric high boiling hydrocarbon materials havingsubstantial gum-forming tendencies when employed as internal combustionengine fuels. The cooled and partially condensed effluent then passesthrough line 48 and is introduced into separator 50 whichi's'preferably'a centrifugal separator of the Webre cyclone type. Hereinthe partial condensate, amounting to a very small part of the totaleffluent, is separated from the vapor and is removed through line 52 ata rate controlled by valve 54 in accordance with liquid level controller56. Flow recorder controller 58, which is adjusted to maintain apredetermined rate of flow of condensate through line 52 operatescoolant bypass valve 60 so that the hot effiuent flowing through line 44is cooled sufiiciently to partially condense the desired proportion ofthe reactor efiluent.

The separator 50 as employed in this specific process was a cylindricalvessel 18 inches inside diameter and 6.0 feet high. The cooled andpartially condensed reactor eflluent was introduced tangentially at apoint 3.0 feet from the bottom, the condensate was removed through anoutlet at the bottom of the vessel, and the non-condensed vapor wasremoved through an outlet conduit 53 which extended from a central pointWithin.

the vessel near the top thereof and downwardly essentially along thevertical axis of the vessel and then through the wall near the bottomthereof. This permits a rapid rotation of the vapor'within the vesselaround the outlet pipe and an effective centrifugal separation of theheavy partial condensate which collects on and flows down the inside'ofthe'vessel' wall. A drip ring 51 was incorporated in. the top ofseparator 50 to prevent condensate entry into outlet pipe 53.

The preferred proportion so condensed is a very minor amount rangingfrom 0.01% up to about 10% by volume. Preferably this proportion isbetween about 0.1% and about and in the experimental verification of thepresent invention it has been found that partial condensaticn of about2.2% by volume is sufficient to substantially eliminate the so-calledheavy ends or polymer from the effluent so as to avoid the usualnecessity for rerun-ningthe depropanized liquid product.

'In the present invention, slightly more than 2% by volume of theeffluent is' condensed and is removed at a rate of 22 barrels per day bymeans of line 62. This material contains some' reformed gasoline boilingbelow about 420 F. and accordingly is returned for redistillation withthe material from which the naphtha feed to the process of thisinvention is prepared. This step, not shown for sake of simplicity inthe drawing, is entirely conventional and effects a recovery ofapproximately 14.5 barrels of reformed gasoline boiling range productboiling below about 420 F. The net polymer production is about 7.5barrels per day.

The uncondensed portion of the diluent flows from cyclone 50 at atemperature of about 450 F. through line 64 and is further cooled andcondensed in interchanger 66 in which heat is recovered by heat exchangewith the hydrogen recycle gas as subsequently described. The condensedeffluent together with the uncondensed hydrogen recycle gas flowsthrough line 68 into product separator 70 in which the uncondensed gasesare separated from the process pro-duct. The reformed naphtha product isremoved through line 72 at a rate of 1100 barrels per day controlled byvalve 74 in response to liquid level controller 76. This liquid is sentby means of line 78 to a conventional depropanizer, not shown, whereinpropane and lighter hydrocarbon gases are separated to produce thereformed naphtha product of this invention. This product is produced ata rate of 1028 barrels per day and has the following properties:

TABLE II Reformed naphtha product Boiling range, F 115-427 APE gravity425.7 Sulfur, weight percent 0.007 Nitrogen, weight percent 0.001 Knockrating (F1+3 cc. TEL) 93.7

AS I'M gum, rug/100 cc 2 The uncondensed portionof the effiuent consistsessentially of the hydrogen-containing recycle gas which is removed fromseparator 70 by means of line 80 and because of the net production ofhydrogen in the process, the excess portion of this is bled from thesystem through line 82 at a rate of 140 MSCF. per day controlled byvalve 84. Part or all of this'gas may be employed as fuel in the firedheaters in the process if desired.

The remaining recycle gas is passed through line 86 and is compressedfro-m 375 p. s. i. g. to 425 p. s. i. g. in recycle gas compressor 88.Part of this compressedrecycle gas is passed as a regenerated catalystpretreating gas through line 100 at a rate of 165 MSCF. per daycontrolled by valve 102 into separator and catalyst pretreating chamber10. This pretreating gas is introduced below cone-shaped baflle 05 andpasses'therefrom downwardly through the annular space within the lowerperiphery of bafile 98 and then directly into the top of the bed ofregenerated catalyst in chamber 10. A first part of this gas passesupwardly through sea-ling leg 99 and pretreating zone 96 countercurrentto the regenerated catalyst. By means of this countercurrent passage ofgas the catalyst is pretreated with hydrogen to reduce the higher oxidesof cobalt and molybdenum formed during regeneration to the lower oxides.The pretreating gas, along with excess regeneration gas coming down fromthe top of the lift line, are removed from eneath bafiie 94 through linecontroilzd by valve 92. The remaining porticn of the pretreating gasintro duced through line 100 and passed downwardly into the top ofreactor 12, passes radially outwardly below the lower periphery ofbaffle 98 and is disengaged from the catalyst bed with the total reactoreffluent in disengaging zone 42 at points around the lower periphery ofbaths 955 and through line 44, and acts as a sea: gas preventing theupfio'w'of reactor effiuent into the pre treating chamber 10. The spentpretreating gas and excess regeneration gas areremoved from separatorchamber 10 at a point below baffle 94 through line 90 at a rate of 205MSCF. per day controlled by valve 92 which in turn is actuated bydifferential pressure controller 104 tovmaintain a positive pressuredifferential between the top and the bottom of catalyst pretreating zone96, that is, the pressure above cone-shaped bafi le 95 is slightly lessthan the pressure below. it and within baffle 98.

The remaining portion of the compressed recycle gas flows at a rateof4120 MSCF. per day through line 106 and is preheated in interchanger 108to 350 F. in exchange with the reactor efiiuent after polymer removal(interchanger 66). I

Of this preheated recycle gas, 4160 MSCF. per day are further heated infired preheater 110 to a temperature of about 950 F. The primaryhydrogen'recycle gas is introduced into engagingzone 30 via line 122 ata rate of 3500 MSCF. per day controlled by valve 124 and controller 126.The remaining 660 MSCF. per day of hydrogen is introduced via line 25controlled by valve 27 into the naphtha transfer line 26.

The spent hydrocarbonaceous catalyst passes downwardly through thecolumn 12 at a rate controlled by solids feeder and stripper 140 whichis provided with a reciprocating tray 142 and a lower stationary tray144 so that upon reciprocation of tray 142 a substantially constantvolumetric withdrawal of spent catalyst uniformly throughout thecross-sectional area of column 12 is achieved. Spent catalyst fromfeeder 140 accumulates as bed 146 which constitutes a surge. volume, thelevel of which rises. and falls asgranular solids are withdrawn from thebottom of the column periodically through outlet 14% controlledby motorvalve 150.-

The spent solids are thus discharged into. pressuring chamber 14 when itis depressured toabout 400' p. s. i. g. causing a displacement ,gas toflow upwardly through outlet 148 into the bottom of reactor 12. A sealgas comprising a mixture of this last-named gas and a small portion ofthe primary recycle gas stream, which .passes downwardly through solidsfeeder 140; is removed from disengaging zone 151 through line 152 at arate of 140 MSCF. per day controlled by valve 154. This gas is mixedwith the spent catalyst pretreating' gas removed from the upper part ofthe column through line 90 and is employed as fuel.

The spent granular solids in pressuring chamber 14 are raised inpressure to 430 p. s. i. g. by the introduction of regeneration recyclegas through manifold 156 upon the opening of valve 153 described below.Following this pressuring step, valve 160 is opened and the pressuredsolids are discharged by gravity into induction chamber 16 to maintainthe downwardly flowing bed 162 of spent granular catalyst to be conveyedand regenerated so as to submerge the lower inlet opening 164 of theregeneration chamber. Level indicator 166 is provided to indicate thesolids level of bed 162.

Valve 160 is then closed, motor valve 168 is then opened, and pressuringvessel 14 is depressured from 430 pounds to about 400 pounds by thedischarge of gas through lines 156 and 170. Valve, 168 is then closedand valve 150 is reopened to remove additional spent catalyst and thesolids pressuring cycle is repeated. The operation of motor valves 150,158, 160, and 168-is controlled in sequence by cycle timer operator 172so as to receive solids, pressure, discharge solids, and depressure at arate sufficient to charge solids into induction chamber 16 at a rate"equal to the solids clrculation rate set by solids feeder 140. I

Referring now to solids pretreater and separator 10, spent regenerationgases collecting in space 174 are removed therefrom through line 176 ata rate of 1612 MSCF. per day and a temperature of ll5 F. This gas ispassed into solids-separator 178 wherein any cata- 1O lyst fineselutriated from the catalyst stream in separator 10 are removed from theregeneration gas recycle. These solids are removed from separator 178 bymeans of line 180.

The hot off gas es continue through line through control valves 171,173, and 175 and any others not shown to provide a pressure dropsufficient to force a fraction of the hot spent regeneration gasesthrough the one or more'intermediate reactor heater zones hereinaftermore' fully described. This serves to cool the hot regeneration zone offgases in steps as they pass through successive reheating zones tomaintain the desired high reaction temperature in reaction zones 32, 36,40, etc. in contacting column 12. The hottest regeneration gas thusheats the reactant vapor nearest the product outlet. In reformingnaphtha this is highly effective since the prodnet is at this pointleast susceptible to high temperature decomposition and a risingreaction temperature can be maintained.

I The thus partially cooled regeneration gas then flows through line 182through heatexchanger 184 in exchange with raw naphtha feed referred toabove and is therein cooled to a temperature of about 640 F. Thistemperature is controlled by temperature recorder controller 186 whichoperates bypass valve 188 so as to control the naphtha heating mediumpassing through interchanger 184. The cooled recycle gas passes throughline 190 and condensate separator 191 and is compressed to 430 p s. i.g. in compressor 192. This recycle gas then flows through line 194 at arate controlled by valve 196 and is divided into a solids pressuringstream flowing through line 198 to pressure solids in chamber 14, and aconveyance-regeneration stream flowing from line 200.

Referring now in Figure l to the reactor reheating zone 34 in contactingcolumn 12, this zone is provided with one or more tubes 161 providedwith fins 163. The fins are preferably vertically disposed within thereactor. The partially cooled reactant vapors pass between the fins andare reheated after being separated from the downwardly moving bed ofcatalyst solids. One or more of such finned tubes are disposed in anopen heat transfer zone located at one or more points within contactingcolumn 12, such as between a pair of parallel plates disposed verticallyand extending substantially across the reactor. One such plate 167 isshown in Figure 1. At the ends of these parallel plates are provided endclosures 169 and 177 providing .an open rectangular chamber open at itsupper and lower ends and containing therein the banks of finned tubesreferred to above. The upper open end of this solids-free heat exchangezone is covered by rounded or gabled cap 179 whereby the downwardlymoving solids are directed around on each side of the reheating zone orzones and move downwardly through a solids flow zone as .a dense bed allaround the heat transfer zone. A

Because the resistance to how of reactant vapors is considerably higherthrough the-downwardly moving mass of solids in the solids flow zonewhich surrounds the above described heat transfer zone, only a minorportion of the rising vapors from first reaction zone 32 pass upwardlythrough the descending solids around each reheating zone .and generatetherein a pressure differential sufiicient to force themajor proportionofthe rising vapors upwardly through the open heat transfer zone andthrough direct contact with the banks of finned tubes shown. The risingvapors arehereby reheated, pass upwardly below cap 179, and thendownwardly past the lower edge of the cap into reengagement with thedownwardly moving solids. The vapors pass upwardly through the nextreaction zone, here designated as zone 36. The temperature of thesereheated vapors is measured at a point just above cap 179 by means ofthermocouple or other means 181. This actuates temperature recordercontroller 183 which in turn regulates hot regeneration gas bypass valveso as steer-.586

11 to maintain the reheated vapors at the desired reaction temperature.

Obviously one or more of these reheating zones may be disposed along thelength of a given reaction zone. The number employed depends of courseupon theextent to which endothermic reactions decrease the temperatureof the reacting vapors and also upon the degree of de viation which canbe tolerated from isothermal or any other desired temperatureconditions. In the present example three such reheating zones wereemployed to raise the temperature of a mixture of naphtha vapor andhydrogen from temperatures of about 890 F. to temperatures of about 930F. in a combined desulfurizing and reforming operation using cobaltmolybdate catalyst.

Referring now to Figure 2, a fragmentary end view taken at right anglesto the view in Figure 1 is shown the reheating system. Equipmentelements which are also shown in Figure 1 are here designated by thesame num bers. The upper gable or cap 179 serving to maintain the emptyspace 165 free of solids is clearly shown, as are the parallel,vertically disposed plates 167 and 167a constituting the sides of thereheating zone. A bank of finned tubes 161 having fins 163 is hereshown. The vapor flow occurring in this system is indicated by thearrows.

Referring again to Figure l and continuing to follow the flow of thepartially cooled regeneration gas recycle, this recycle gas then flowsthrough line 182 through heat exchanger 184 in exchange with raw naphthafeed referred to above and is therein cooled to a temperature of about640 F. This temperature is controlled by temperature recorder controller136 which operates bypass valve 188 so as to control the quantity ofregeneration gas passing through interchanger 184. The cooled recyclegas passes through line 190 and condensate separator 191 and iscompressed to 430 p. s. i. g. in com presser 192. This recycle gas thenflows through line 194 at a rate controlled by valve 196' and is dividedinto a solids pressuring stream flowing through line 198 to pressuresolids in chamber 14, and a regeneration stream flowing from line 200.

An oxygen-containing gas, such as air is introduced via line 202. It iscompressed to 433 p. s. i. g. in compressor 204 and is introduced at arate of 123 MSCF. per day controlled by valve 206 in response to oxygenrecorder controller 208 for combination with the compressed regenerationrecycle gas flowing through line 260. The combined oxygen-containingregeneration gas, which may contain from about 0.1 to about oxygen andpreferably from 0.5 to 5.0% oxygen, then passes at a temperature ofabout 256 F. and at a rate of 1735 MSCF. per day through line 210tangentially into the upper portion of regenerator heat exchange zone212. This zone is contained within the annulus between the lower portionof regeneration conduit 18 and jacket 214 which surrounds concentricallythe lower portion of the regeneration conduit. The regeneration gaspasses downwardly through zone 212 and is preheated therein by means ofthe exothermic heat of regeneration liberated within the lower part ofregeneration zone 18 to a temperature of about 706 F. This preheated gasis injected directly into induction chamber 16 'at a point below thelevel of the spent catalyst to be conveyed, it passes into inlet 164 ofthe regeneration zone, and then upwardly therethrough at a ratesufficient to effect upflow regeneration of the spent catalyst.

The regenerated solids discharge at outlet 216 against cap 215 whichapplied a force against the solids stream issuing from the outlet tomaintain the catalyst solids during regeneration as a moving mass havinga density substantially equal to the static bulk density. Theregenerated catalyst is discharged against b'affie 215 which applies aforce against the mass of catalyst issuing from regeneration conduit 18and maintains the, upwardly 12 moving catalyst at a bulk densitysubstantially equal to the static bulk density thereof.

As stated above, the major part of the coke burn-oil from the catalystoccurs in the lower orfirst part of the regeneration zone and asubstantial part of this endo thermic heat is transferred through theregeneration conduit wall to preheat the regeneration gas recycle and tokeep the inner regeneration conduit wall 217 cool. All of the netendothermic heat of regeneration however is removed as sensible heat inthe regeneration recycle, with the exception of usual heat losses, andmost of it is recovered in heating the reactor and preheating the feed.

The spent granular catalyst is substantially completely regeneratedwhile passing upwardly through the upflow regeneration conduit and isdischarged from outlet opening steer the regeneration conduit intoseparator chamber 10 previously described.

Because of the fact that the granular catalyst is maintained as a denseupwardly moving compact bed substantially at the static bulk density ofthe catalyst, the upward velocity and accordingly the residence time ofthe spent catalyst in the regeneration system'is not limited by theheight of the regenerator or by the velocity 'of the regeneration fluidcirculated therethroughpas is the case in the conventional gas-lift orsuspended solids systems. Once the regeneration fluid rate is sufficientto exceed the opposing forces of gravity and friction on the moving bed,the catalyst will move as continuously fed at the inlet and removed fromthe outlet and at a flow rate determined by solids feeder zone 14-0. Any

necessary increases in regeneration fluid rate .to remove heat from thesystem have absolutely no effect whatsoever upon the rseidnce time ofthe catalyst in the system or the degree to which itis regenerated andthe only external effect is one of a somewhat increased pressure.difierentiaL. i

Accordingly in the present process the spent catalyst may be completelyregenerated by the removal of the entire quantity of hydrocarbonaceousdeactivating materials during an upflow regeneration. In the presentexample, this is accomplished by utilizing an oxygen concentration ofabout 2.0% at the inlet of the regeneration zone. The spent catalystanalyzes about 4.1% carbon and is discharged into separator 10 afterregeneration analyzing less than about 0.05% carbon, the restoration ofactivity is essentially In the apparatus of this invention, the entirestructure above grade level is about 55 feet in height, the reactorcolumn diameter is 4 feet 6 inches, and the regeneration conduit is14-inch schedule 40 pipe. The catalyst is-circulated at a rate of 10.3tons per day and moves at an upward velocity of 15 feet per hour throughthe regeneration conduit. This low velocity is totally impossible tomaintain in a gas-lift or pneumatic conveyor system and herein itpermits the complete regeneration of the catalyst during the liftingstep. conveyors and sealing legs have thus been eliminated.

It is not intended that the above detailed description of the process ofthis invention as applied to cobalt molybdate reforming anddesulfurization of gasoline be considered limiting because the treatingprocess hereinabove described may just as'well and with comparableadvantageous results be applied to any solids-fluid contacting processinvolving a catalyst ,or other contact ma.- terial, an elevated reactiontemperature, an exothermic regeneration, and a net endothermic contactreaction.

A particular embodiment of the present invention has been hereinabovedescribed in considerable detail by way of illustration. It should beunderstood that various other modifications and adaptations thereof mayhe made by those skilled in this particular art without departing from ithe spirit and scope of this invention as set forth in the appendedclaims.

I claim:-

1. In a solids-fluid contacting process wherein a stream It is obviousthat all ing heat to said reactant fluid therein surrounding saidreheating Ito reheat said fluid thereby cooling fluid, injecting freshregeneration with regeneration the cooled *zojne through which thereactant of granular solid contact material is recirculated generallydownwardly through a fluid contacting zone and then upwardly as a movingbed through a solids conveyance regeneration zone, a reactant fluid ispassed through said contacting zone in direct contact with said contactmaterial therein, a conveyance-regeneration fluid is recirculatedupwardly through said conveyance-regeneration zone at a rate sufficientto maintaina substantial pressure gradient therein and therethrough andto regenerate it, and a force is applied against the regeneratedmaterial discharging therefrom to, maintain it at a bulk densitysubstantially equal to its static bulk density, the improvement whichcomprises passing at least part of said regeneration-conveyance fluidfrom the outlet of said conveyance-regeneration zone through a closedcyclic path external to said conveyance-regeneration zone, decreasingthe pressure of the circulating fluid in said external path at at leastone point therein thereby forcing at through at least one reheating zonewithin said contactleast part of said fluid ing zone in indirect heatexchange relation with the reac'tantfluid only and out of contact with.said solids'which surround said reheating zone thereby cooling saidregeneration fluid to recover at least part of heat of regenerationcontained as sensible heat therein and supplypassing through saidcontacting zone, adding additional regeneration fluid to the cooledregeneration fluid, passing the cooled regeneration fluid through aregenerationfluid preheating zone in indirect heat exchange with atleast the first part of said conveyance-regeneration zone to absorb heatof regeneration therefrom, and injecting the preheated fluid into theinlet'of said conveyance-regeneration zone to convey and regenerate saidcontact material.

2. In a solids-fluid contacting process wherein a moving bed of granularsolid contact materialis passed downiwardly by gravity through acontacting zone, a fluid is passed therethrough atcontrolled conditionsof temperature, pressure and composition in direct contact with saidmoving solids bed to eflect an endothermic reaction therev by formingspent solids, said spent solids are passed upwardly as a moving bedthrougha solids conveyance regeneration zone concurrently with arecirculating regeneration fluid at regeneration conditions oftemperature,

pressure, and composition and at a rate sufficient to generate asubstantial pressure gradient therein to convey said bed of solids, saidupwardly moving bed is maintained at substantially the solids staticbulk density by applying a force to the bed of regenerated solidsissuing from said conveyance-regeneration zone, and said solids arereturned for repassage through said contacting zone, the improvement inremoving the heat generated during the regeneration of said solids andsupplying the endothermic heat of reaction in said contacting zone whichcomprises disengaging hot regeneration fluid from the regeneratedsolids, passing it through a closed cyclicpath external-to saidconveyance-regeneration zone, dropping the pressure of said hotregeneration fluid at at least one point in said path therebyforcing atleastpart of'said fluidthrough at least one reactant reheating zonewithin said contacting zone out of direct contact with said solids zoneas a downwardly moving dense bed and in indirect heat exchange relationwith the fluid passing therethrough and at a rate sufficient said hotregeneration fluid into admixture fluid, and injecting the fluid mixtureinto said conveyance-regeneration zone to convey and regenerate saidupwardly moving bed of solids thereby maintaining a recirculating streamof conveytrnce-regeneration fluid directly through said regenerationzone and indirectly through said contacting zone.

' 3. A process according to claim 2 wherein said reactant reheating zonecomprises a solids free heat exchange fluids flow in contact to conveysaid material wherein a moving bed of drocarbon. conversion zone,.therethrough at hydrocarbon conversion conditions of with'heat exchangesurfaces, and a solids flow zone sin rounding the heat exchange zonethrough which said solids pass by gravity in dense moving bed form.

4. A process according to claim2 in combination with a plurality of saidreactant reheating zones spaced apart from one another in saidcontacting zone, said fluid being contacted passing successively in saidcontacting zone through an alternate series of reaction zones and heatexchange zones, said solids passing successively through file of saidfluid passing through said contacting zone.

6. In an ,endothermic hydrocarbon conversion process solid hydrocarbonconversion catalyst is passed downwardly by gravity through a byahydrocarbon is passed temperature, pressure, and composition in directcontact with saidcatalyst to form converted hydrocarbons and spentcatalyst solids deactivated by a hydrocarbonaceous deposit, said spentcatalyst ,is passed upwardly as a moving-bed through a catalystconveyance-regeneration zone concurrently with an oxygen-containingconveyance-regeneration gas at catalyst regeneration conditions oftemperature, pressure, and composition at a rate sufficient to generatea substantial pressure gradient therein to conveynsaid bed of catalyst,a force is applied against the regenerated catalyst dischargingtherefrom to maintain said upwardly moving bed substantially at thecatalysts static bulk density, andsaid regenerated catalyst is returnedfor repassage through said hydrocarbon conversion zone, the improvementin maintaining said hydrocarbon conversion zone at the desiredtemperature and cooling the conveyance regeneration zone which comprisesmaintaining at least one hydrocarbon reheating zone containing aparallel heat exchange and solids flow zone within said hydrocarbonconversion zone, passing the solid catalyst downwardly through alternatereaction zones and solids flow zones and passing saidhydrocarbon throughalternate reaction zones and heat exchange zones in said contactingzone, dizengaging hot spent regeneration gas from the regeneratedcatalyst, recirculating said regeneration gas in a closed cyclic pathexternal to said regeneration zone,- decreasing the pressure of said gasat least once in said closed cyclic path thereby forcing at least partof said gas to flow through each heat exchange zone in indirect heatexchange relation with said :hydrocarbon only and out of heat exchangerelationship with said solids thereby partially cooling saidregenerationgas and reheating the endothermally cooled hydrocarbonreactant, removing partially cooled regeneration gas from the heatexchange zone, adding fresh regeneration gas containing oxygen thereto,and introducing the mixture thus formed into saidconveyance-regeneration zone to maintain the regeneration gas recycle,

7. .A process according to claim 6 wherein said hydro:

carbon conversionis a'reforming reaction, said catalyst is cobaltmolybdate, said hydrocarbon is a petroleum naphtha, said gas introducedvinto said conveyance-regeneration zone comprises flue gas containingbetween about 0.1% and about 10% of oxygetnsaid conversion condi- -tionsof temperature, pressure and composition are, re

spectively, 700 F. to 1200 F., 50 p. s. i. g. to 2000 p. s. i. g., and500 to 10,000 s. c. f. of hydrogen per barrel of naphtha, and aplurality of said hydrocarbon reheating zones are disposed along thelength of said hydrocarbon conversion zone.

8. In a process for the endothermic conversion of hydrocarbon wherein amoving bed of solid granular hydrocarbon conversion catalyst is passeddownwardly by gravity through a hydrocarbon conversion zone, hydrocarbonconversion conditions of temperature, pressure,

and composition are maintained therein while a hydrozone, said spentcatalyst is conveyed-to the top of said conversion zone andsimultaneously regenerated by passing it upwardly as a moving bedthrough said conveyanceregeneration zone concurrently with a flow of anoxygencontaining conveyance-regeneration gas, and said catalyst 3 ismaintained substantially at its static bulk density in i said upwardlymoving bed by applying a force against the mass of regenerated catalystdischarging from said conveyance-regeneration zone, the improvementwhich comprises maintaining a plurality of hydrocarbon reheating zonesspaced apart from one another along the length of and within saidconversion zone,'said reheating zone comprising a solids free heatexchange zone surrounded by a solids flow zone, said solids thus passingdownwardly through said conversionzonethrough alternate reaction andsolids flow zones, said hydrocarbon passing through said conversion zonethrough alternate reaction and reheating zones, maintaining arecirculation of said conveyance-regeneration gas generally downwardlythrough a closed cyclic path external to said conveyance-regenerationzone and upwardly through said conveyance-regeneration zone to conveyand regenerate said spent catalyst and to adsorb as sensible heat theheat liberated during regeneration by the steps of disengaging hot spentregeneration gas from the bed of regenerated catalyst, successivelydecreasing the pressure of said conveyance-regeneration gasin pluralsteps in said cyclic path thereby passing at least part of said gassuccessively through each of said heat exchange zonesin indirect heatexchange relation with the hydrocarbon flow therethrough but out ofheatexchange relationship with the surrounding solids to recover theheat of regeneration thereby cooling said regeneration gas and supplyingthe endothermic heat of hydrocarbon conversion in said contacting zone,further "cooling the thus partially cooled-regeneration gas in theexternal path, separating any condensate formed during the lattercooling step, compressing the cooled gas to a pressure substantiallyequal to that of said hydrocarbon, conversion zone plus the pressuredifferential maintained 1:

between the inlet and the outlet of said conveyanceregeneration zone,adding suflicient oxygen-containing gas to the compressed gas to providea conveyance-regeneration gas containing between about 0.5% and 5.0% ofoxygen, and passing said conveyance-regeneration gas l6 engagingchamber, means adjacent, said outlet to apply a force against solidsdischarging-therefrom to maintain them insaid conduit substantially attheir static bulk density, means for passing a fluid through saidcontacting column, afluid outlet for disengaged fluid from saidfluiddisengaging chamber, a return conduit forming a closed cyclic pathfor recirculating regeneration gases external to and then through saidconveyance-regeneration conduit, and fluid conduit means communicatingwith into the bed of spent pressured catalyst, submerging the inlet ofsaid conveyance-regeneration zone in said in'duction zone whereby saidgas recirculates into said inlet and flows upwardly through saidconveyance-regeneration zone;

9. A process according to claim 8 in combination with the step ofpassing a parrot said cooled compressed gas into said pressuring zone toraise the pressure of gasesin the interstices of sure substantiallyequal to that in said conversion zone by'an' amount substantially equalto the pressure differential existing between the inlet and the outletof said conveyance-regeneration zone.

10. In an apparatus for contacting a fluid with a recirculating streamof granular solid contact material including at successively lowerlevels a solidsreceiving and fiuid 'clisengaging chamber, a co ntactingcolumn, a solids pressuring chamber, and a solids induction. chamber; anelongated conveyance-regeneration conduit communicating attits inletwith a low point in said-induction chamber and at itsoutlet with saidsolids-receiving and fluid disr the spent catalyst therein from apressaid solids pressuring chamber for the introduction and removal offluids, the improvement which comprises at least one gas pressuredecreasing means disposed in said return conduit to decrease thepressure of gases flowing therethrough, at; least one finned-tube heatexchange means disposed within. said contacting column, said lastnamedmeansbeing connected in fluid receiving relation to said pressuredecreasing means, and means for diverting the downward flow of solidsout of contact'with said heat exchange means whereby said heat exchangemeans contacts only the fiuids flowing through said contacting columnand is out of contact with said solids.

11. An apparatus accordingto claim 10 wherein said heat exchange meanscomprises a chamber surrounding said finned tubes and which is open atits top and bottom for fluid flow therethrough, a cap superimposed abovesaid chamber and adapted to divert the downwardly flowing bed of solidsaround the top of said chamber, and means for diverting the solids flowaway from direct contact with the inlet and outlet conduits of said heatexchange means which pass through the space between the outside of saidchamber and the inside of said contacting column.

l2. In an apparatus for the treatment of a fluid stream I throughcontact with a moving bed of'solid granular co n' tact material whichcomprises, a contacting apparatus structure adapted to confine saiddownwardly moving bed ,and provided at successively lower levels with asolids-receiving and fluid-disengaging chamber, a fluidsolids contactingchamber, a solids pressuring chamber,

and an induction chamber, an elongated conveyance-re-- generationconduit communicating at its inlet opening with a low point in saidinduction chamber and at its outlet opening with said solids-receivingand fluid disengaging chamber, and a means, at said outlet openingadapted to apply a force against the mass of contact materialdischarging therefrom to maintain the solids mov ing in saidconveyance-regeneration conduit substantially at their static bulkdensity, the improvement which comprises a plurality of bundles ofexternally finned heat transfer tubes disposed at spaced intervals alongthe length of and within said contacting'chamber, an enclosuresurrounding each of said bundles and open at its top and bottom forfluid flow, a cap superimposed upon each of said enclosures adapted todivert solids flow down and around said enclosure while permitting fluidflow from the top thereof whereby said fluid flows through saidenclosure in direct contact with said finned tubes and said solids flowaroundsaid enclosure out of direct contact therewith, a regenerationfluid recycle conduit opening from saidsolids-receiving andfluid-disengaging chamber, a plurality of valves disposed in saidconduit, the

inlet of each of said bundles of finned tubes being connected totheupstream end of one of said valves, the outletof eachof said bundlesbeing connected to the downstream end of the corresponding valve, afluid compressand means for mixing fresh regeneration fluid withsaid'seco'nd part of. said compressed fluid:

.13; An apparatus according to claim l2 in combina- 17 tion with atemperature sensitive element disposed within said contact columndownstream from said bundle of finned tubes, and an instrument meansresponsive to said element and connected to actuate said valve so as tovary the quantity of regeneration ofi-gas flowing through'said bundle offinned tubes.

References Cited in the file of this patent UNITED STATES PATENTS BergJuly 27,

1. IN A SOLIDS-FLUID CONTACTING PROCESS WHEREIN A STREAM OF GRANULARSOLID CONTACT MATERIAL IS RECIRCULATED GENERALLY DOWNWARDLY THROUGH AFLUID CONTACTING ZONE AND THEN UPWARDLY AS A MOVING BED THROUGH A SOLIDSCONVEYANCE REGENERATION ZONE, A REACTANT FLUID IS PASSED THROUGH SAIDCONTACTING ZONE IN DIRECT CONTACT WITH SAID CONTACT MATERIAL THEREIN, ACONVEYANCE-REGENERATION FLUID IS RECIRCULATED UPWARDLY THROUGH SAIDCONVEYANCE-REGENERATION ZONE AT A RATE SUFFICIENT TO MAINTAIN ASUBSTANTIAL PRESSURE GRADIENT THEREIN AND TO CONVEY SAID MATERIALTHERETHROUGH AND TO REGENERATE IT, AND A FORCE IS APPLIED AGAINST THEREGENERATED MATERIAL DISCHARGING THEREFROM TO MAINTAIN IT AT A BULKDENSITY SUBSTANTIALLY EQUAL TO ITS STATIC BULK DENSITY, THE IMPROVEMENTWHICH COMPRISES PASSING AT LEAST PART OF SAID REGENERATION-CONVEYANCEFLUID FROM THE OUTLET OF SAID CONVEYANCE-REGENERATION ZONE THROUGH ACLOSED CYCLIC PATH EXTERNAL TO SAID CONVEYANCE-REGENERATION ZONE,DECREASING THE PRESSURE OF